Our tour guide, Gabriele, was wonderful. He did everything within his power to make it a great experience. HOWEVER, the crowds are so overwhelming that you feel like you are in a moving mosh pit for the entire tour. As you move from gallery to gallery, the traffic moves in one pattern. There is no going back or lingering. This is not the fault of the tour guide or Viator. It is the Vatican's decision to cram as many people as possible into a day. Other museums control the numbers entering and exiting. This element was very disappointing. If an individual was claustrophobic, they would have a difficult time enduring this experience.
Being able to go to the head of the line was a big plus as the line to purchase tickets went on forever.

If you have your heart set on heading atop the Eiffel Tower, this is the only way to do it. The lines to ascend the Eiffel Tower are very, very long to take the only working elevator. With Skip the Line, you have an escorted tour (we had ten people in our party) you go to the front of the line! We learned amazing things about the tower and had an opportunity to learn and see so much about Paris.
This is well worth the cost of the ticket, especially if you are in Paris for a short time.